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A novel method for severe plastic deformation at high strain rate

Harishchandra Lanjewar (UGent) , Leo Kestens (UGent) and Patricia Verleysen (UGent)
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Abstract
Severe plastic deformation (SPD) processing is defined as any method of forming under an extensive hydrostatic pressure that may be used to impart a very high strain to a bulk solid without any significant change in dimensions of the sample, producing exceptional grain refinement. Most of the SPD techniques employ very low processing speeds, however increased deformation rates are known to have a significant effect on the final microstructure. Most of the SPD processes operating at high rates do not impose hydrostatic pressures to the material and can therefore only be used for very ductile materials, while in others, the microstructural changes are limited to the surface layers of the material. To circumvent these restrictions a novel facility has been designed and developed where high hydrostatic pressures are maintained while a high shear deformation is imposed at high strain rates. The device combines the features of a high pressure torsion (HPT) unit with the principle of a torsional split Hopkinson bar (SHB) setup. A small ring-like sample, placed between two molds, is first subjected to a high, static pressure and subsequently to a high speed shear deformation upon release of torsional energy stored in a long bar. Although, the principle is rather straightforward, the design of the setup was extremely critical because of the high forces and energies involved. Tests have been performed on commercially pure aluminum. The material hardness increased in accordance with the microstructure and processing conditions; viz. annealed, only compressed and applied shear strain. Deformed grains departed from equiaxed shape and showed morphological texture in the direction of the shear even at very low strains indicating the presence of shear strains in the material. Further the material, or more specifically its mechanical properties and microstructure evolution is compared with conventional, statically deformed HPT samples.
Keywords
severe plastic deformation, dynamic high pressure torsion, mechanical properties, microstructure

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Chicago
Lanjewar, Harishchandra, Leo Kestens, and Patricia Verleysen. 2018. “A Novel Method for Severe Plastic Deformation at High Strain Rate.” In , ed. E. Buzaud, A. Cosculluela, H. Couque, and E. Cadoni. Vol. 183. EDP Sciences.
APA
Lanjewar, H., Kestens, L., & Verleysen, P. (2018). A novel method for severe plastic deformation at high strain rate. In E. Buzaud, A. Cosculluela, H. Couque, & E. Cadoni (Eds.), (Vol. 183). Presented at the DYMAT 2018 - 12th International Conference on the Mechanical and Physical Behaviour of Materials under Dynamic Loading , EDP Sciences.
Vancouver
1.
Lanjewar H, Kestens L, Verleysen P. A novel method for severe plastic deformation at high strain rate. In: Buzaud E, Cosculluela A, Couque H, Cadoni E, editors. EDP Sciences; 2018.
MLA
Lanjewar, Harishchandra, Leo Kestens, and Patricia Verleysen. “A Novel Method for Severe Plastic Deformation at High Strain Rate.” Ed. E. Buzaud et al. Vol. 183. EDP Sciences, 2018. Print.
@inproceedings{8573795,
  abstract     = {Severe plastic deformation (SPD) processing is defined as any method of forming under an
extensive hydrostatic pressure that may be used to impart a very high strain to a bulk solid without any
significant change in dimensions of the sample, producing exceptional grain refinement. Most of the SPD
techniques employ very low processing speeds, however increased deformation rates are known to have a
significant effect on the final microstructure. Most of the SPD processes operating at high rates do not
impose hydrostatic pressures to the material and can therefore only be used for very ductile materials, while
in others, the microstructural changes are limited to the surface layers of the material. To circumvent these
restrictions a novel facility has been designed and developed where high hydrostatic pressures are
maintained while a high shear deformation is imposed at high strain rates. The device combines the features
of a high pressure torsion (HPT) unit with the principle of a torsional split Hopkinson bar (SHB) setup. A
small ring-like sample, placed between two molds, is first subjected to a high, static pressure and
subsequently to a high speed shear deformation upon release of torsional energy stored in a long bar.
Although, the principle is rather straightforward, the design of the setup was extremely critical because of
the high forces and energies involved. Tests have been performed on commercially pure aluminum. The
material hardness increased in accordance with the microstructure and processing conditions; viz. annealed,
only compressed and applied shear strain. Deformed grains departed from equiaxed shape and showed
morphological texture in the direction of the shear even at very low strains indicating the presence of shear
strains in the material. Further the material, or more specifically its mechanical properties and
microstructure evolution is compared with conventional, statically deformed HPT samples.},
  articleno    = {03008},
  author       = {Lanjewar, Harishchandra and Kestens, Leo and Verleysen, Patricia},
  editor       = {Buzaud, E. and Cosculluela, A. and Couque, H. and Cadoni, E.},
  isbn         = {9782759890538},
  issn         = {2100-014X},
  language     = {eng},
  location     = {Arcachon, France},
  publisher    = {EDP Sciences},
  title        = {A novel method for severe plastic deformation at high strain rate},
  url          = {http://dx.doi.org/10.1051/epjconf/201818303008},
  volume       = {183},
  year         = {2018},
}

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